000 AXNT20 KNHC 182353 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED AUG 18 2010 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM 11N-25N ALONG 29W MOVING W AT 10-15 KT. LOW-LEVEL CYCLONIC FLOW IS NOTED IN GLOBAL MODEL GUIDANCE AND SATELLITE IMAGERY IN THE VICINITY OF THE WAVE AXIS BETWEEN 25W-35W. THIS WAVE ALSO COINCIDES WITH MAXIMUM VALUES OF DEEP LAYER MOISTURE INDICATED ON TOTAL PRECIPITABLE WATER IMAGERY FROM 05N-27N E OF 34W. CONVECTION REMAINS EMBEDDED WITHIN THE ITCZ REGION S OF 15N DUE TO THE SAHARAN AIR LAYER AND AFRICAN DUST LOCATED N OF 15N. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 10N-13N BETWEEN 29W-35W. TROPICAL WAVE EXTENDS FROM 11N-26N ALONG 40W MOVING W AT 15 KT. OVERSHADOWED BY THE WAVE TO THE EAST...THE WAVE REMAINS SHROUDED IN A SAHARAN AIR LAYER SUPPRESSING CONVECTIVE ACTIVITY. ANY ASSOCIATED CONVECTION IS MORE RELATED TO THE ITCZ AND WILL BE DISCUSSED IN THE ITCZ SECTION. TROPICAL WAVE EXTENDS FROM NEAR 10N77W TO JAMAICA NEAR 18N78W THEN TO THE CENTRAL BAHAMAS NEAR 24N76W MOVING W AT 15-20 KT. BROAD LOW-LEVEL CYCLONIC FLOW IS NOTED IN THE VICINITY OF THE WAVE AXIS FROM THE SW CARIBBEAN SEA NORTHWARD TO OVER CUBA AND PORTIONS OF THE FLORIDA STRAITS. LOW-LEVEL MOISTURE IS MAXIMIZED ACROSS THE CARIBBEAN BETWEEN 72W-82W AS DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY THIS EVENING. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 09N-24N BETWEEN 73W-84W. MUCH OF THIS ACTIVITY IS FURTHER ENHANCED BY AN UPPER LEVEL TROUGH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 11N75W TO THE YUCATAN CHANNEL NEAR 22N85W. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 12N15W 13N27W 12N40W 08N53W 09N61W. WITH A MONSOONAL TROUGH IMPACTING MUCH OF THE ITCZ REGION ACROSS THE TROPICAL ATLC...SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 09N-15N BETWEEN 16W-26W. ISOLATED MODERATE CONVECTION IS ELSEWHERE FROM 04N-13N BETWEEN 09W-45W. ...DISCUSSION... GULF OF MEXICO... A PAIR OF UPPER LEVEL ANTICYCLONIC CIRCULATIONS...ONE CENTERED OVER THE WESTERN ATLC NEAR 34N67W AND THE OTHER CENTERED OVER NORTH TEXAS NEAR 32N98W ARE PROVIDING THE GULF AND FLORIDA PENINSULA WITH EAST-NORTHEASTERLY UPPER LEVEL FLOW. WATER VAPOR IMAGERY INDICATES DRY UPPER LEVEL AIR IS LOCATED E OF 89W... HOWEVER...WARM AIR ADVECTION ON SOUTHWESTERLY LOW-LEVEL WINDS... DAYTIME INSTABILITY AND SEABREEZE DYNAMICS OVER INTERIOR FLORIDA ARE GENERATING ISOLATED SHOWERS AND TSTMS N OF 26N E OF 89W AND AREAS E OF 84W S OF 26N...INCLUDING PORTIONS OF THE FAR SW FLORIDA PENINSULA. THE INSTABILITY LOCATED OVER THE EASTERN GULF IS LARGELY DUE TO THE WEAKNESS BETWEEN THE TWO UPPER LEVEL ANTICYCLONES TO THE NORTH AND AN UPPER LEVEL TROUGH AXIS LOCATED OVER THE NW CARIBBEAN SEA COUPLED WITH A TROPICAL WAVE STRETCHING ITS IMPACTS FROM OVER CUBA INTO THE SE GULF WATERS. FARTHER WEST...A MID-LEVEL CIRCULATION OVER LOUISIANA AND STATIONARY FRONTAL BOUNDARY IS ANALYZED OVER THE LOWER MISSISSIPPI RIVER VALLEY AND NORTH TEXAS PROVIDING FOR SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE NW GULF N OF 25N W OF 89W. THE PREVIOUSLY MENTIONED UPPER LEVEL TROUGH AXIS OVER THE NW CARIBBEAN IS ENHANCING ONGOING SCATTERED SHOWERS AND TSTMS OVER THE WESTERN YUCATAN PENINSULA THAT STRETCH THEIR IMPACT WESTWARD TO 92W THIS EVENING. CARIBBEAN SEA... A TROPICAL WAVE EXTENDS FROM NORTHERN COLOMBIA TO THE CENTRAL BAHAMAS AND CONTINUES IMPACTING MUCH OF THE WESTERN CARIBBEAN WITH SCATTERED SHOWERS AND TSTMS. MOST OF THE STRONGEST CONVECTION IS LOCATED BETWEEN 73W-84W...INCLUDING HAITI... JAMAICA...AND CUBA. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING ACROSS THE REMAINDER OF THE WESTERN CARIBBEAN... INCLUDING INTERIOR PORTIONS OF CENTRAL AMERICA. THIS LARGE AREA OF SHOWER ACTIVITY IS FURTHER SUPPORTED BY A NARROW UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM NORTHERN COLOMBIA NEAR 11N75W TO THE YUCATAN CHANNEL NEAR 22N85W. CONVECTION LOCATED IN THE SW CARIBBEAN AS SCATTERED SHOWERS AND ISOLATED TSTMS ARE PRIMARILY DUE TO SURFACE CONVERGENCE NEAR A PORTION OF THE ITCZ EXTENDING ACROSS SOUTHERN COSTA RICA ALONG 10N TO NEAR 10N78W. FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED IN THE TROPICAL N ATLC NEAR 18N58W AND EXTENDS AN UPPER LEVEL TROUGH AXIS FROM THE UPPER LEVEL LOW TO 12N61W THEN WESTWARD TO 13N69W. MOSTLY DRY NORTHERLY UPPER LEVEL FLOW COVERS THE BASIN E OF 70W DUE TO THIS FEATURE AND IS MAINTAINING OVERALL FAIR WEATHER AT THE SURFACE. ATLANTIC OCEAN... AN UPPER LEVEL ANTICYCLONE IS CENTERED NORTH OF THE DISCUSSION AREA NEAR 34N67W AND IS PROVIDING MUCH OF THE W ATLC N OF 24N W OF 55W WITH NE TO E UPPER LEVEL FLOW AND OVERALL DRY CONDITIONS ALOFT. THIS UPPER LEVEL PATTERN CONTINUES TO SUPPORT A 1021 MB HIGH CENTERED NEAR 27N67W AND A 1022 MB HIGH CENTERED NW OF BERMUDA NEAR 35N66W. WEDGED IN BETWEEN THESE HIGH CENTERS IS A SURFACE TROUGH ANALYZED ALONG 30N BETWEEN 60W-67W. ISOLATED SHOWERS ARE OCCURRING FROM 28N-30N BETWEEN 57W-70W. FARTHER WEST...A FEW ISOLATED SHOWERS ARE FROM 29N-32N BETWEEN 74W-79W. A COLD FRONT EXTENDS FROM 33N48W TO 31N55W ACROSS THE CENTRAL ATLC WITH ISOLATED SHOWERS LOCATED WITHIN 90 NM EITHER SIDE OF THE FRONT. MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO ADVECT SW FROM THE FRONTAL BOUNDARY GENERATING WIDELY SCATTERED SHOWERS FROM 20N-28N BETWEEN 55W-62W. THIS MOISTURE IS LOCATED NW OF AN UPPER LEVEL LOW CENTERED OVER THE TROPICAL NORTH ATLC NEAR 18N58W. EAST OF A LINE FROM 32N49W TO THE UPPER LEVEL LOW... WATER VAPOR IMAGERY INDICATES A VERY DRY AND SUBSIDENT ENVIRONMENT DUE TO A VERY BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 25N38W. THIS UPPER LEVEL ANTICYCLONE SUPPORTS A 1023 SURFACE HIGH CENTERED SOUTH OF THE AZORES NEAR 35N27W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN